Wow, that IS a deep question. I can give an answer that may sound sort of simplistic, but it will at least get the conversation started, and you can reply from there. Obviously I'll be answering from the perspective of a Christian.

As simply as I can put it, the meaning of life is to be like God by being in relationship with Him. But now it will take me several books to explain that. I'll still try to keep it brief, and let your questions guide me before I write a wall of text.

God created people in his image (Gn. 1.27-27). He made us to be like him. We will find our meaning in life as we form a relationship with God where He makes us like Himself. But let me fill that out a little bit.

In Genesis 1, people were created in God's image to rule the earth and subdue it. God is really the ruler of the earth, but humans were made to rule it with him (co-regency). We are to take care of the earth, be responsible in our use of it, and to use our knowledge about the earth (science) to become wise and to care for it well. So part of the meaning of life (being like God in relationship with Him) is to be like God in treating the earth responsibly and in learning all we can about it. We find meaning there.

In Genesis 2 those thoughts are developed further. We discover that the man and the woman are put in the Garden "to work it and take care of it." Interestingly, both of these words are priestly words, not agricultural ones. Humans are given the role of serving in sacred space (which implies a relationship with God). They find meaning in having a healthy relationship with God and in caring for sacred space (the earth). We're not slaves to meet the needs of the gods (a common ancient Near Eastern idea), we're not meaningless agglomerations of chemicals. Ultimately God wants to be in relationship with us as we live in his presence. We will find meaning there.

Based on this text, we also find meaning in productive work and moral responsibility. Part of being in healthy relationship with God and being like him is to do meaningful things with our lives (work) and do be good and godly people while we do it (like God Himself). Back to what we said before, we use science and our knowledge to care for the earth and each other, to do meaningful work in moral relationships with each other, all of which reflects that we are like God, and we relate to Him the same way. This is the meaning of life.

David taught the same things in the Psalms; Jesus taught the same things in the Gospels, and Paul teaches the same things in his letters. Romans 8.29 says that it's God's intent that we all be conformed to the likeness of His Son, Jesus. We know from Matthew 5.17 that Jesus was the fulfillment of the Law, meaning that Jesus lived in relationship with God and was like him in all His fullness. The Law of Moses was a temporary measure to tell people how to live—that they should have certain attitudes. He did that by commanding actions with the idea that they would see the attitudes behind them. They failed. Jesus, on the other hand, preached the attitudes (Matthew 5), but more importantly, lived an an example of the proper attitudes (Philippians 2.5-8), as well as the proper actions (John 8.46). So now we're supposed to follow Christ's example: Be like Jesus, and in that way we will be like God and be in relation with Him. That is the meaning of life: To Be Like Jesus.

So, enough for all the theology stuff. What about the practical part? Let me try it this way.

1. I've already established that true meaning can only be found in a relationship with Jesus. That has to be the foundation of all the points that follow.2. We find meaning in our work (Ecclesiastes 5.18). We are become responsible participants in our society.3. We find meaning in our relationships, and our healthy relationships bring meaning to life.4. We find meaning in morality—in being good people and in doing what is right. Otherwise life is just full of deceit and wrong-doing.5. We find meaning in serving other people—in caring for the poor, the lonely, the imprisoned, the homeless, and the orphans and widows.6. We find meaning in learning as much as we can (science), in advancing knowledge and progress, and therefore in understanding our world and ourselves.

I could go on and on, but I don't want to bury you with too much information at this point. Read what I've said, ask your questions, and that way I can focus which direction I go in from here.